The invention relates to a method of and apparatus for determining a position of a land vehicle wherein a position determined from driving data is corrected in accordance with control data stored in a memory.
A system has been developed (Electronic Traffic Pilot for Automobile Drivers) which gives recommendations for an optimal driving route on the basis of the existing road network, the instantaneous position of the vehicle, and the origin and destination data. The reliability of this system depends among other things on the accuracy with which the instantaneous position of the vehicle can be determined.
Method and apparatuses for determining the position of a land vehicle which determine and evaluate only driving data such as travel distances and driving direction by using principles of dead reckoning position finding suffer from a loss of location after longer driving distances, which can lead to an erroneous recommendation. By repeated correction in the form of matching with data of a stored, digitized road network, this loss of location can be kept within limits such that the reliability of the recommendation is not impaired. However, in carrying out the matching, problems can occur which are based e.g. on the density of the road network, the limited memory space of the computer arrangement present in the vehicle, or the computing time required by the computer.
If the road network is very dense and the matching is carried out only at long intervals of space and time due to the required computing time, the position finding inaccuracy can accumulate in the meantime to the extent that the position determined from the driving data is indeed to be assigned to the road network, but this road network deviates from the actual position, and the matching is then made to the wrong street. It is not desirable to limit to a thinned out road network, since the system is required to issue recommendations between optional positions of origin and destination. Accordingly, it must be possible to take into account a region in the order of magnitude of a federal state or of the entire federal territory of the Federal Republic of Germany.